Strapping device and method for operation thereof

ABSTRACT

A device for strapping lying stacks of printed products with a strap, as well as to a corresponding operating method. The device includes a handling device with two press jaws for pressing together and conveying the stack in a conveyor direction running in the stack longitudinal direction, from a stack formation region into a strapping region, as well as a strapping unit with a stack rest and with a strap channel. The strapping unit is traversable in an ejection direction running transversely to the conveyor direction. The strap channel is arranged in a plane orientated perpendicularly to the ejection direction. The strap channel includes a movable channel section, so that the strap channel may assume an open and a closed condition, wherein a stack in the open condition may be brought in the conveyor direction into a strapping region enclosed by the strap channel.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention lies in the field of further processing of printed products and relates to a device for strapping lying stacks of printed products, with a strap, as well as to a corresponding operating method.

2. Description of Related Art

In the printing industry, intermediate products and part products as, for example, individual sections of newspapers or magazines, which are printed before other sections, signatures from which books are to be later manufactured, or individual sheets, pamphlets, smaller brochures, part sheets etc., which are later to be added to newspapers or magazines as supplements or collectors parts, must be intermediately stored between their manufacture and further processing, and for this must be transported within the operation and, as the case may be, from one operation to another operation. For quite some while, the arrangement of the intermediate products in lying stacks, so called bar-stacks, and the storage and transport of these in a stacked manner, for example on pallets, has been tried and tested for such intermediate storage and transport.

Usually, these stacks have a length (perpendicular to the surface of the printed products), which is significantly larger than the edge lengths of the printed products. It is therefore the case of stacks which are not stable, also not in a perpendicularly standing manner, without aids. The length of the stacks is, for example, matched to the dimensions of the pallets, on which they are stacked, and with which they are transported and stored, which means that the stacks are usually 120 or 150 cm long and comprise for example 200 to 300 printed products. The stacks are layered on one another in a lying manner on the pallets, and thus, form storage units which may be handled in a simple and space-saving manner with generally common warehouse vehicles.

The end-sides of the stacks are usually stabilized with end-plates, for example small wooden planks, which are matched to the format of the stacked products. The stacks are held together in the pressed condition by way of a strapping with a strap, which for example consists of plastic. The strapping runs over the longer edges of rectangular printed products. Depending on the product format, one straps in the middle once or twice. With two strappings, these divide the end-surfaces into three roughly equal parts.

The lying stacks are usually manufactured by way of rowing products standing on an edge, by way of double-sided stabilisation of the rowed products by way of end-plates and by way of subsequent pressing and strapping. For the strapping, the separated stacks provided with end-plates are held by a handling unit, and are conveyed in the stack direction into a strapping region where, as the case may be, they are also displaced transversely to the stack region. In the strapping region, a loop of the strap is presented by way of a strap channel and is firmly pulled around the stack. The stacks are conveyed away after the strapping.

Devices for strapping lying stacks of printed products are, for example, known from the publications EP 0623542, WO 2004/009448 (EP 1523443), EP 1380506 and U.S. Pat. No. 6,782,678. They are basically based on two different alternative concepts:

Either—as with EP 0623542 or U.S. Pat. No. 6,782,678—the strapping unit, in particular the strap channel, is stationary, and the strap channel has a movable channel section, which for example, lowers below the conveyer surface or is laterally displaced. This design permits the conveying of a stack in the opened condition into the strapping region enclosed by the strap channel, and the subsequent closure of the strap channel for the actual strapping. Such devices are basically suitable for the strapping at a single strapping position (single strapping). If several strappings are to be applied, the handling unit yet needs to be designed in a displaceable manner transversely to the conveyor direction.

According to the other concept which is described in WO 2004/009448 or EP 1380506, the strapping unit is displaced relative to the stack or to the strapping region. The strap channel is always closed, so that the loop may already be applied, whilst the strapped stack is conveyed away and a new stack is conveyed into the strapping region. Subsequently, the strap channel is moved into the strapping region by way of displacement, transverse to the stack conveyor direction. Advantages with respect to the first concept lie in reducing the cycle duration since the loop may be formed already when conveying the stack into the strapping region. Moreover, there is flexibility with regard to the number and the position of the strappings. Disadvantages are the relatively large masses which need to be moved in a short time over relatively large distances, since usually the strap channel together with a stack rest and, as the case may be, further components for storage of a strap supply roll, as well as for the drive and the fastening/welding of the strap, form a common movable unit.

It is the object of the invention to further develop a known strapping device, such that one may achieve a greater flexibility with regard to the position of the strappings and the course of the strapping process.

The strapping device, in a manner known per se, comprises a handling device with two press jaws for pressing together and conveying the stack in a conveyor direction running in a stack longitudinal direction, from a stack formation region into a strapping region, as well as a strapping unit with a stack rest and a strap channel. The strapping unit is traversable in an ejection direction running transversely to the conveyor direction. The strap channel, thereby, is arranged in a plane orientated perpendicular to the ejection direction. By way of the movement transverse to the conveyor direction, it may be applied around the strapping region, wherein the stack rest is then located below the strapping region, as well as also arranged laterally thereto. Here, that space region, in which the stack is located when the strapping takes place, is indicated as the strapping region. The strapping region, for example, is set by way of a certain position of the press jaws and/or by a guide device for the press jaws. According to the invention, the strap channel has a moving channel section, so that the step channel may assume an open and a closed condition. A stack, thus, in the open condition of the strap channel may be introduced in the conveyor direction into the region enclosed by the strap channel, and may be brought into the strapping position. The strapping may then take place in the closed condition.

Although, in view of the displaceability of the strapping unit, it does not appear to be necessary to design the strap channel in a controllable manner, i.e. with a movable channel section, this feature in combination with a displaceable strapping unit has the following surprising advantages:

-   -   several operating modes are possible, which in each case may be         optimised with regard to certain parameters, such as e.g. energy         consumption or short cycle time: If only one single strapping is         to be attached, the strapping unit may remain in a stationary         manner around the strapping position. The strap canal is         connected, i.e. the movable channel section is opened for         introducing the stack, and then closed again. The energy         consumption and the wear are reduced by way of this, since the         massy strapping unit is not moved. If a multiple strapping is to         be made, the strap channel is first brought into a first         strapping position and then into a second strapping position. It         then remains preferably in the second strapping position and the         subsequent stack is firstly strapped at the second position and         then at the first position. In this manner, the necessary travel         (travel path transverse to the conveyor direction) and thus         likewise the wear and the energy consumption may be reduced. In         the case that the cycle duration is to be reduced, the channel         in both cases may also remain closed and the strapping unit with         a respectively large travel may be traversed transversely         between a strapping position and a rest position. In the rest         position, the stack may be transported past the closed strap         channel and into the strapping region.     -   the movement of the strapping unit transverse to the conveyor         direction may be utilised, in order to simultaneously achieve         two effects: On the one hand the strap channel is traversed         between two different positions (different strapping positions         or strapping/rest positions). A large flexibility with respect         to the position and number of strapping results by way of this.         Since preferably the stack rest may also be co-moved, the         strapped stack may already be moved a certain distance in the         ejection direction, as soon as it has been released from the         handling unit. Likewise, the cycle duration may be reduced and         the movement of the strapping unit may be used in a dual manner,         by way of this.

The method according to the invention comprises the following steps, which do not necessarily need to be carried out in the specified sequence:

-   -   a) feeding the stack in a conveyor direction which runs in a         stack longitudinal direction, from the stack formation region         into the strapping region;     -   b1) traversing the strapping unit in or opposite to the ejection         direction, in order to bring the strap channel to at least one         strapping position, in which it encompasses the strapping         region;         and/or     -   b2) opening the movable channel section should the strap channel         with step a) already be located in a strapping position, and         closure of the movable channel section after step a);     -   c) strapping the stack at at least one strapping position;     -   d) traversing the strapping unit and/or the stack in the         ejection direction, in order to bring the strapped stack into a         least one release position, in which it is located laterally         from the strapping unit in the ejection direction.

As already mentioned, the strapping device may advantageously assume a part of the ejection movement of the stack, and by way of this, simultaneously release the strapping region for the purpose of feeding a new stack.

In an advantageous further formation of the invention, the stack rest itself is designed for actively or passively moving the stack in the ejection direction independently of the traversability of the strapping unit, i.e. by way of a conveyor unit being present for the stack (actively) or by way of the stack rest comprising means which prevent the friction in the ejection direction (passively). Particularly preferably, a roller carpet with rollers which are arranged transversely to the ejection direction and as the case may be are driven, are applied

Suitable drives which preferably are controlled by a common control unit, are present for moving the strap channel or the strapping unit, of the movable channel section and the handling unit. The operating mode may be set in the control unit, so that this initiates the corresponding movements of the mentioned unit. Preferably, the control device controls the drive for the strapping unit in a manner such that this is traversed in the ejection direction, by less than a stack width.

BRIEF DESCRIPTION OF THE DRAWINGS

Examples of the invention are represented in the drawings and are described hereinafter. In a purely schematic manner there are shown in:

FIG. 1-5 a strapping device according to the invention, on strapping a stack, in several momentary views;

FIGS. 6 and 7 a strap channel with a movable channel section, in the opened or closed condition.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1-5 show a strapping device 1 according to the invention on strapping a stack 2. The strapping device 1 comprises a stationary carrier frame 3, on which the following components to some extent are movable: a strapping unit 10 with a stack rest 20 and with a strap channel 30; a handling unit 40 for the stack 2; and intermediate storage 50.

The handling unit 40 comprises two press jaws 42, which are mounted on a carrier 41 and which may accommodate a stack between them in a clamping manner. The carrier 41 is linearly displaceably mounted in a conveyor direction F, which here runs perpendicularly to the plane of the drawing, in a guide 44 attached on the carrier frame 3. The press jaws 42 may also be displaced relative to the carrier 41, also in a horizontally running direction A, perpendicularly to the conveyor direction, by way of a suitable guide 43. This direction is here called the ejection direction A, since it corresponds to the direction, in which the stack 2 is moved after the strapping. The handling unit 40 is designed such that the stack 2 may be received in a stack formation region which is not shown here, and may be moved into a strapping region U. The strapping region U is that strapping region, in which the stack 2 is located on strapping. The strapping unit 10 may assume different positions relative to this, which hereinafter are called strapping position(s) or rest position(s). The stack 2 itself may likewise assume different positions relative to the strapping region U, in particular on with the feed conveying and the conveying away.

Details of the handling unit and the stack formation, which may likewise be realised here, are to be deduced for the initially mentioned WO 2004/009448.

The strapping unit 10 comprises a stack rest 20 and a strap channel 3, which are mounted on a carriage 12 which may be traversed by way of rollers 13. The carriage 12 is traversable in the ejection direction A within the stationary parts of the carrier frame 3. Suitable guides which are not shown, are present for this. A supply roll 15 for strap is mounted on the carriage 12 by way of a mounting, and is moved together with the strapping unit 10. The stack rest 20 is formed by a horizontal carpet of rollers 22 lying next to one another, whose axes point in the conveyor direction F. The upper sides of the rollers 22 define a rest surface 23 which lies in a rest plane E and which is arranged directly below the strapping region U or borders on its lower limitation surface or coincides with this. The rollers 22 are driven by a drive 24, here in the form of a drive belt which is guided over several deflections and which cooperates with the rollers 22 with a friction fit.

The strap channel 30 is vertically orientated, wherein the plane defined by it runs parallel to the conveyor direction F. FIGS. 6 and 7 show a view of this plane. The strap channel 30 has a roughly U-shaped stationary channel section 22 as well as a roughly straight movable channel section 34, with which the channel 30 may be closed (FIG. 7) or opened (FIG. 6). As FIGS. 1-5 show, the strap channel 30 or its stationary section 32 is stationary relative to the stack rest 20. The moving section 34 may be lowered downwards with its own drive, below the stack rest 20, in order to open the canal 30. In the closed condition, a loop of a strap may be introduced into the channel 30 by way of means which are not shown here, and firmly pulled around the stack 2 and connected. The rollers 22 of the roller carpet for this are distanced from one another in the region of the strap channel 30.

The intermediate storage 50, whose rest surface 53 is likewise formed by a carpet of rollers 52 lying next to one another and lies in the same plane E as the rest surface 23 of the stack rest 20, also belongs to the stationary components of the strapping device 1. A gap 4 whose width b changes by way of moving the strapping unit 10 or may even be completely closed, is located between the two rest surfaces 23, 53. A drive device 16, which here comprises a stack rest 20, 50 which is stationary or is movable about rollers 22, 52, as well as a belt 19 led around a further roller 17, serves for moving the strapping unit 10 in the ejection direction A. The further roller 17 is movable in a vertical guide 18, for which a drive which is not shown in more detail is provided. The strapping device 10 may be pulled to the stationary intermediate storage 50 by way of moving the further roller 17 downwards, so that a continuous rest surface 23, 53 is formed (FIG. 5). The strapping device 10 is preferably mounted, in particular biased, such that it returns back to its initial position when the tensile stress is reduced by way of the belt 19 of the drive device 16. The belt 10 is preferably designed such that it may accommodate the weight of a stack 2. Thus, the rest surfaces 23, 53 and the upper belt face of the belt 19 form a continuous rest surface of a variable width.

The function of the strapping device 1 is described hereinafter. Thereby, different operating variants are also explained.

FIGS. 1 and 2 show the strapping unit 10 at a first strapping position U1, at which the plane of the strap channel 30 intersects the strapping region U, which is located in a defined position from the stationary guide 44 of the handling unit 40, roughly in the middle. The strap channel 30 is open in FIG. 1, i.e. the movable channel section 34 lowers below the rest surface 23. The stack 2 is brought by the handling unit 40 through the opening of the strap channel 30 into the strapping region U, but is not yet let go off. The stack lower side is located on or shortly above the rest surface 23, wherein the weight, to large extent, is accommodated by the handling unit 40. The movable channel section 34, as shown in FIG. 2, is subsequently traversed upwards and the channel 30 is closed. The strapping (single strapping) may take place in this position U1. Hereby, the press jaws 42 are also strapped. Subsequent to the strapping, the press jaws 42 are pulled back in the horizontal guide 43, and the strapped stack 2 is applied onto the stack rest 20. The respective position of the press jaws 42 is such as is represented in FIG. 4 for the case of a multiple strapping. For releasing the stack 2, the rolls are driven 22 and convey the stack 2 along the rest surface 23 and over the belt 19 to the intermediate storage 50.

If the cycle duration is to be optimised, with the stack release, the complete strapping unit 10 is moved in the ejection direction A, until the rest surface 23 of the stack rest 20 merges into the rest surface 53 of the intermediate storage 50. The respective position of the strapping unit 10 is such as is represented in FIG. 5 for the case of multiple strapping. The strap channel 30 is here located outside the strapping region U at a rest position R1, so that simultaneously a new stack 2 may be brought into the strapping position without opening the strap channel 30. During this, a loop may be applied in the strap channel 30. The carriage 12 is subsequently traversed back again, in order to move the strap channel 30 back into the strapping position U1 again. The ejection movement of the strapped stack 2 here is combined in an advantageous manner with a movement of the strap channel 30 into an idle position R1.

FIGS. 3 and 4 show a variant of the outlined method for creating a multiple strapping at two strapping positions U2, U3 which are arranged essentially mirror-symmetrically to the middle plane of the stack 2. The strapping unit 6 is pushed only with such a small travel that the strap channel 30 is located at one of the strapping positions U2, U3. In FIG. 3 the stack, similarly to in FIG. 2 with the open strap channel, has been brought into the strapping region U, and the strap channel 30 subsequently closed. A first strapping takes place in the strapping position U2. Subsequently, the strapping unit 10 is pushed opposite to the ejection direction A, so that the strap channel 30 is positioned at the further strapping position U3 (FIG. 4). The two-fold strapped stack 2 after release by the handling unit 40, by way of actuating the rollers 22, is conveyed from the stack rest 20 to the intermediate storage 50. The channel 30 is opened and a new stack 2 is fed and strapped in the reverse sequence U3-U2. The travel of the strapping unit (change of the distance b) here is always smaller than a stack width. Thereby, the reduced energy requirement is advantageous.

FIG. 5 shows a modification of the method according to FIGS. 3 and 4, with which the strapping unit 10 after the double strapping is displaced so far, that the width b of the gap 4 is reduced to zero, and the strap channel 30 is located at an idle position R1 outside the strapping region U. This operating mode, again, has the advantage that the loop may be presented in the strap channel 30, which remains closed.

It is possible for no stationary intermediate storage 50 to be present, or for the stationary intermediate storage 50 and the moving stack rest 20 to be connected to one another at each point in time and in each position 12 of the carriage 12 by way of an intermediate piece or end-piece of variable width. For example, the roller carpet may be designed in a continuous manner, wherein the end which is at the front in the ejection direction may be deflected downwards, so that the rest surface 23, 53 always ends at the same location in space.

It is also possible to modify the device such that the stack is ejected to further sides or in further directions, e.g. to the side on which the handling location is located. 

1. A device for strapping lying stacks of printed products with a strap, comprising a handling device with two press jaws for pressing together and conveying the stack in a conveyor direction running in the stack longitudinal direction, from a stack formation region into a strapping region, as well as a strapping unit with a stack rest and with a strap channel, wherein the strapping unit is traversable in an ejection direction running transversely to the conveyor direction, and wherein the strap channel is arranged in a plane orientated perpendicularly to the ejection direction, said strap channel comprising a movable channel section, so that the strap channel may assume an open and a closed condition, wherein when said strap channel is in the open condition, a stack may be brought in the conveyor direction into a strapping region enclosed by the strap channel.
 2. The strapping device according to claim 1, further comprising a first drive for moving the handling device in the conveyor direction, a second drive for moving the strapping unit in the ejection direction, and a third drive for moving the movable channel section so as to opening and closing the strap channel.
 3. The strapping device according to claim 2, further comprising a control device for controlling the drives.
 4. The strapping device according to claim 1, wherein the strapping unit is traversable in the ejection direction by less than a stack width.
 5. The strapping device according to claim 1, wherein the stack rest is adapted to move the stack in the ejection direction in an active or passive manner, said stack rest comprising a roller carpet of driven and/or freely rotatable rollers that are arranged transversely to the ejection direction.
 6. The strapping device according to claim 1, further comprising a stationary intermediate storage for strapped stacks (2), said stationary intermediate storage, in the ejection direction, is arranged laterally of the stack rest.
 7. The strapping device according to claim 6, wherein the strapping unit may be displaced such that the rest surfaces of the stack rest and of the intermediate storage border one another and are aligned with one another in the ejection direction.
 8. The strapping device according to claim 1, wherein the handling unit comprises a linear guide arranged in the conveyor direction and along which the press jaws are traversable, wherein the press jaws are displaceable transversely to the linear guide, to release the stack.
 9. A method for strapping a stack, with a device according to claim 1, comprising the steps of: step a) feeding the stack in a conveyor direction running in the stack longitudinal direction, from the stack formation region into the strapping region; step (b) selected from the group of steps consisting of: b1) traversing the strapping unit in and/or opposite the ejection direction, in order to bring the strap channel to at least one strapping position, in which the strapping channel encloses the strapping region; and, b2) opening the movable channel section, should the strap channel following step a) already be located in a strapping position, and closing the movable channel section after step a); step c) strapping the stack at at least one strapping position; and, step d) traversing the strapping unit and/or the stack in the ejection direction, in order to bring the strapped stack into at least one release region, in which it is located laterally of the strapping region in the ejection direction.
 10. The method according to claim 9, wherein the strapping unit, after strapping the stack (2) at a first strapping position, is displaced relative to the stack, such that the strap channel is arranged at a second strapping position, and such that the stack is strapped afresh at the second strapping position.
 11. The method according to claim 10, wherein the strap channel, after step d), remains in the second strapping position, the movable channel section is opened for feeding a further stack and subsequently closed again, and the further stack is firstly strapped at the second strapping position and, subsequently, by displacing the strapping unit, is strapped at the first strapping position.
 12. The method according to claim 9, wherein the strapping unit in the ejection direction is traversed maximally by less than a stack width.
 13. The method according to claim 9, wherein the stack, after the strapping is released by the handling unit, is supported from below by the stack rest.
 14. The method according to claim 10, wherein the strapping unit in the ejection direction is traversed maximally by less than a stack width.
 15. The method according to claim 11, wherein the strapping unit in the ejection direction is traversed maximally by less than a stack width.
 16. The method according to claim 10, wherein the stack, after the strapping is released by the handling unit, is supported from below by the stack rest.
 17. The method according to claim 11, wherein the stack, after the strapping is released by the handling unit, is supported from below by the stack rest.
 18. The method according to claim 12, wherein the stack, after the strapping is released by the handling unit, is supported from below by the stack rest. 